I am very pleased with these nipples. I have had a lot of trouble with nipples. they either come out way to fast or don't want to come out at all. I've even had every nipple I owned at one time keep collapsing on my son while he was trying to eat. It was very frustrating until I bought these nipple. I have to say if I would have bought these to begin with I would have save myself time, money, and trouble.